Why Multi-Agent Systems Need Both MCP and A2A in 2025

Why Multi-Agent Systems Need Both MCP and A2A in 2025 In 2025, the conversation around AI agents has shifted from "can an agent call a tool?" to "how do many agents work together reliably in production?" That shift matters. Single-agent demos are easy to build. Production systems are not. Once an agent has to coordinate with other agents, call external tools, preserve boundaries, and stay observable under failure, architecture becomes the difference between a demo and an operating system. This post explains one practical way to think about that architecture: MCP for agent-to-tool communication A2A for agent-to-agent communication Observability for making the whole system debuggable and operable If you are building autonomous systems, this separation is one of the cleanest design choices you can make. The 2025 shift: from isolated agents to interoperable systems Google introduced the Agent2Agent (A2A) protocol in April 2025 as an open protocol for agent interoperability, with support fr